Roll forming is a well-known method for making useful articles from sheet metal. Roll forming is commonly used to make pipes for such uses as heating and air conditioning ducts, fittings for pipes, and flanges.
Conventional roll-forming machines generally include at least one pair of juxtaposed forming rollers. To roll form sheet metal with convention roll-forming machines, the forming rollers are rotated and a piece of sheet metal is fed between the forming rollers so that the sheet metal is drawn through the nip between the forming rollers. The forming rollers are configured to impart a shape to the sheet metal drawn therebetween by bending or folding the sheet metal. Conventional roll-forming machines often include a multitude of pairs of such forming rollers positioned in series. With these larger more complicated roll-forming machines, the sheet metal is generally fed through the nip between the first pair of forming rollers so that the sheet metal is then drawn through the entire series of forming rollers.
After production, roll-formed sheet metal products are normally marked to indicate the manufacturer and size thereof. Size marking is necessary for manufacturers, wholesalers, and retailers to keep track of inventory, and for end users to select the correct size of sheet metal product and corresponding fittings.
One conventional method of marking sheet metal products is ink marking. The manufacturer and size of the sheet metal product is simply marked on the surface of the sheet metal product with ink. This method of marking is unsatisfactory for the following reasons. First, the ink tends to smear and rub off easily during handling of the sheet metal product. In addition, ink marking of sheet metal products requires an additional labor step after the production of the sheet metal product which increases the cost of the sheet metal product.
Another conventional method of marking sheet metal products is packing the sheet metal products in appropriately-marked boxes. This method of marking is also unsatisfactory because of the additional expense of the labeled box and the additional labor step required after the production of the sheet metal product. In addition, once the sheet metal product is taken out of the box, the sheet metal product is no longer easily identified.
Still another method of marking sheet metal products is bundling sheet metal products of the same size and tying the bundle together with a strap which indicates the manufacturer and size of the sheet metal products in the bundle. This method of marking sheet metal products is also unsatisfactory because of the additional expense of the marking strap and the additional labor step required to bundle and strap the sheet metal products after production. In addition, as with the method of boxing the sheet metal products, the sheet metal products are not easily identified after the sheet metal products are unbundled.
Therefore, there is a need for a method of permanently marking roll-formed sheet metal products which is also cost effective.